Configuration for high availability

This configuration consists of a single messaging engine, running in a cluster, that can fail over to one or more alternative servers. A high availability configuration ensures that there is always a messaging engine running in the cluster, so that messages are always transmitted.

There are two ways to achieve this configuration:

There is no workload sharing in the high availability messaging engine configuration, because there is only one messaging engine to handle the traffic through the destination.

The following diagram shows a high availability messaging engine configuration in which the single messaging engine ME, with a data store, is running in a cluster of three servers. Each server is on a separate node, so that if one node fails, the servers on the remaining nodes are still available.

Each server in the cluster contains the messaging engine configuration, and creates an instance of the messaging engine so that the instance is ready to be activated if another server fails.

The message store for the messaging engine must be accessible by all the servers in the cluster. For a data store, the way to achieve this depends on the data store topology you use. If you use a networked database server, you must ensure that the database server is accessible from all servers in the cluster that might run the messaging engine. Alternatively, you can use an external high availability framework to manage the database by using a shared disk.

Initially, the messaging engine runs in its preferred location of server1.

Figure 1. Highly available messaging engine configuration
The diagram is described in the surrounding text.

The following diagram shows what happens if server1 fails. The messaging engine is activated on the next server in the preferred servers list, which is server2.

Figure 2. Highly available messaging engine configuration after server1 fails
The diagram is described in the surrounding text.

The following diagram shows what happens if server1 and server2 fail. The messaging engine is activated on server3, because this is the only available server.

Figure 3. High availability messaging engine policy configuration after both server1 and server2 fail
The diagram is described in the surrounding text.

If you use messaging engine policy assistance and the high availability messaging engine policy, the list of preferred servers is set up automatically.

If you do not use messaging engine policy assistance and you want the messaging engine to use preferred servers, you must specify one or more preferred servers for the messaging engine. Whenever a preferred server is available, the high availability manager (HAManager) runs the messaging engine in it. When no preferred server is available, the messaging engine runs in any other available server. You can also set the Fail back option on the policy so that when a preferred server becomes available again, the HAManager moves the messaging engine back to it.

If you use messaging engine policy assistance and the high availability messaging engine policy, the messaging engine is not set to fail back.




Related concepts
Policies for service integration
High availability
High availability messaging engine policy
Related tasks
Configuring high availability and workload sharing of service integration
Adding a cluster as a member of a bus
Related information
High availability messaging engine policy
Concept topic Concept topic    

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Last updatedLast updated: Feb 6, 2014 8:11:25 PM CST
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